Helpless,
I'm sorry for your deep hurt and pain and maybe as some others have suggested you need to see your doctor. It's nothing to be ashamed of that you are having a hard time dealing with this.
I appreciate what Nandina said and I might suggest you take this a step further. Sit with yourself and a cup of tea and a journal. Reflect back and write down some instances where there was chaos in your home with your son. All those things, drugs, anger, punched holes in the walls, disrespect, name calling, police at your front door at any time of night, etc. were all the same things I experienced with one of my son's in particular. About 3 years ago I started journaling and put down a huge list of things my sons used to do and when I'm feeling that pit in my stomach because it's too hot outside, too cold outside and I worry about my younger son living in his car 24/7, this helps remind me of what I never, ever want to experience again. I did this not to remember the bad things about them but to bring me back to reality. We mothers tend to remember the little boy with the scuffed knee, floppy hair and red cheeks that used to come in from playing and running with friends outside. But the world and life has changed them and although you must remember the good it's important not to be naive and think they are like they used to be. Sadly, often times, it's just not the case anymore.
If nothing has changed with your son..then nothing will change. YOU must be the change. Push through the hurt. Fake it until you make it. Eventually, you will have moments where you feel "ok" and those moments will lengthen as you become healthier and take the focus off your son and back on to you. Treat yourself with loving kindness.
You can and will get through this. Sending hugs.